The present invention relates generally to equipment used to set the operational height of lawnmowers and other turf maintenance equipment.
Height adjustment mechanisms in the turf maintenance industry generally require tools, removal and insertion of mechanical parts. These and other applications require that the height adjustments be made at discreet intervals. Existing methods to accomplish the height adjustment needed to control the height of grass cut typically use one of two general methods. The first method uses two parallel plates, oriented in a vertical plane, each plate having a series of holes. One plate is attached to the cutting unit, the other plate is attached to castors, rollers, or other similar devices that control the height of the grass cut. During operation, the plates are held in general proximity to one another by a pin or other fastener extending between the two plates. The relative position of the plates, and consequently the height of cut, may be changed by removing the fastener and then lifting, or lowering, the cutting unit to the desired height. When the desired height is reached, the fastener is reinserted into a hole or holes closest to the desired height. This method requires removal and reinsertion of a mechanical device to accomplish the height adjustment. Additionally, the height adjustment is relatively imprecise; that is, the fastener holes are located at fixed intervals requiring the cutting unit to conform to the corresponding height intervals.
The second method uses a rod or shaft, oriented vertically, retained against the frame of the cutting unit. The lower end of the shaft is connected to a castor, roller, or similar device. The shaft can be raised or lowered relative to the frame and held in place by mechanical fasteners such as nuts, stacked spacers, or threaded hardware when the rod is also threaded. This method requires use of tools to remove and replace the mechanical fasteners. Alternatively, the stacked spacer configuration requires removal or replacement of the spacers to adjust the height and results in a relatively imprecise height adjustment.
The present invention for controlling the height of the cut grass generally addresses these problems typically found on lawnmowers or other turf maintenance equipment. The present invention allows the cutting unit of the lawnmower or turf maintenance equipment to be raised or lowered more precisely relative to the generally horizontal plane of the ground and the grass without the use of tools or mechanical fasteners or other devices that must be removed and reinserted.
It is an object of the present invention to provide a new and improved apparatus that is not subject to the foregoing disadvantages by providing an improved apparatus for more precisely controlling the height of grass cut by lawnmowers as well as the operational height of other turf maintenance equipment without the use of tools or removal and replacement of mechanical hardware.
The foregoing object of the present invention is provided by an improved height adjustment apparatus for turf maintenance equipment having a ground contacting support and a frame supporting an operational unit. In the case of lawnmowers the operational unit is a cutting unit. It is understood that present invention will also have application to other turf maintenance equipment such as lawn sweepers, lawn rakes, aerators, and other similar equipment. The height adjustment apparatus includes a frame bracket that is attached to the frame with no relative movement therebetween, and a threaded rod threaded through a threaded central bore in a frame bracket. The threaded rod has a nut attached at the upper end thereof and a swivel head attached to the lower end, with the swivel head being attached to the ground contacting support. The swivel head has a substantially smooth bore that receives the threaded rod. The portion of the threaded rod in contact with the swivel head is free from threads and is substantially smooth. The thread-free end of the threaded rod is then free to rotate relative to the swivel head during the height adjustment operation. The height adjustment apparatus further includes a socket having a central bore, the socket being configured to slidably receive the nut and the frame bracket and means for preventing rotation of the socket relative to the nut and the frame bracket. A biasing means is provided for slidably biasing the socket into a non-rotational aspect relative to the frame bracket. It is understood that the socket can be held in non-rotational engagement with the frame bracket by mechanical means or by manufacturing the socket with sufficient mass such that gravity holds the socket engaged with the frame bracket.
In one embodiment of the present invention the means for preventing relative rotation between the socket and nut and the socket and the frame bracket may be providing the socket with generally the same cross section as the nut and the frame bracket. Another means for preventing relative rotation may be providing generally complementary cross sections to the upper end of the socket and the nut and generally complementary cross sections to the lower end of the socket and the frame bracket.
A height adjustment apparatus in accord with the present invention may be operated by moving the socket directionally away from the frame bracket against the force of the biasing means a distance sufficient to allow the socket to disengage from the frame bracket. During this operation, the socket remains slidably engaged with the nut with no rotational movement relative to the nut. When the socket slidably disengages from the frame bracket, the socket can then be rotated, wherein the rotation of the socket causes the nut and threaded rod to rotate in the selected direction. The rotation of the threaded rod causes the rod to engage the threads of the frame bracket; that is, rotation of the threaded rod results in the rod being screwed further in or out relative to the fixed position of the frame bracket and the frame itself. The movement of the rotating rod causes the distance between the frame bracket and the swivel head to change, thus changing the height of the cutting unit relative to the ground contacting support. Because the height of the cutting unit relative to the ground determines the height of the cutting, altering the distance between the frame bracket and swivel head will either increase or decrease the height of the grass cut. This height adjustment operation is accomplished without use of tools or removal and insertion of mechanical parts. The precision of the height adjustment operation is limited only by the thread spacing of the threaded rod and the profiles of the socket, nut and frame attachment.
In another embodiment of the present invention, the rod is threadably engaged with the swivel head while rotationally engaged with the frame bracket. The rod is prevented from vertical translation relative to the frame bracket. This vertical retention function is accomplished by, for example, a differential in the rod""s diameter with the larger diameter portion being captured between two portions of the frame bracket.
To accomplish the height adjustment operation in this embodiment, the socket is moved directionally away from the frame bracket against the force of the biasing means a distance sufficient to allow the socket to disengage from the frame bracket. During this operation, the socket remains slidably engaged with the nut with no rotational movement relative to the nut. When the socket slidably disengages from the frame bracket, the socket can then be rotated, wherein the rotation of the socket causes the nut and threaded rod to rotate in the selected direction. In this embodiment, the rotation of the threaded rod causes the rod to engage the threads of the swivel head; that is, rotation of the threaded rod results in the rod being screwed further in or out of the swivel head, relative to the fixed position of the rod, frame bracket and the frame itself. The movement of the rotating rod causes the distance between the frame bracket and the swivel head to change, thus changing the height of the cutting unit relative to the ground contacting support.
The foregoing objects of the invention will become apparent to those skilled in the art when the following detailed description of the invention is read in conjunction with the accompanying drawings and claims. Throughout the drawings, like numerals refer to similar or identical parts.